1. FIeld of the Invention
The present invention relates to a racing catamaran.
More particularly, the present invention relates to a stable racing catamaran with hydrofoil qualities.
2. Description of the Prior Art
In the case of a body moving through a fluid for which the measured pressure distribution nearly agrees with the perfect-fluid theory, the influence of viscosity at high Reynolds numbers is confined to a very thin layer in the immediate neighborhood of the body.
If the condition of no slip were no to be satisfied in the case of a real fluid there would be not appreciable difference between the field of flow of the real fluid, as compared with that of a perfect fluid.
The fact that at the body the fluid adheres to it means, however, that frictional forces are retarding the motion of the body in a thin layer near the body. In that thin layer, the velocity of the fluid increases from zero at the body (no slip) to its full value which corresponds to the external frictionless flow. This layer is called the boundary layer.
The decelerated fluid particles in the boundary layer do not, in all cases, remain in the thin layer which adheres to the body along the whole wetted length of the body. In some cases, the boundary layer increases its thickness considerably in the downstream direction and causes the flow in the boundary layer become reversed. This causes the decelerated fluid particles to be forced outward, which means that the boundary layer becomes separated from the body. We then speak of boundary-layer separation.
This phenomenon is always associated with the formation of vortices and with large energy losses in the wake of the body. Behind the body there exists a region of strongly decelerated flow (wake), in which the pressure distribution deviates considerably from that in a frictionless fluid. The large drag on such a body can be explained by the existence of this large deviation in pressure distribution, which is in turn, a consequence of boundary-layer separation.
Boundary layer separation reduces the lifting properties of a body moving through a fluid. At small angles of incidence (up to about 10.sup.0), the flow does not separate on either side of the body and closely approximates frictionless conditions. With increasing incidence there is danger of separation on the suction side of the body, because the pressure increase becomes steeper. For a given angle of incidence, of about 15.sup.0, separation will occur.
The separation point is located fairly closely behind the leading edge of the body moving through the fluid and its wake contains a large "dead-water" area. The frictionless, lift-creating flow pattern has now become disturbed, and the drag on the body has become very large. The beginning of separation nearly coincides with the occurrence of maximum lift of the body.
Separation is mostly an undesirable phenomenon because it entails large energy losses. For this reason methods have been devised for the artificial prevention of separation. The simplest method, from the physical point of view, is to move the body through the fluid with the stream in order to reduce the velocity difference between them, and hence to remove the cause of boundary layer formation to begin with.
In later years, suction was successfully used to increase the lift on bodies. Owing to suction on the upper surface near the trailing edge of the moving body the flow adheres to the body at considerably larger angles of incidence than would otherwise be the case. Stalling is delayed, and much larger maximum-lift values can be achieved.
Numerous innovations for racing catamarans have been provided in the prior art that are adapted to be used. Even though these innovations may be suitable for the specific individual purposes to which they address, they would not be suitable for the purposes of the present invention as heretofore described.